In general, an injection molding machine includes an injection device that injects a molten resin into a mold. In this case, in the injection device, a heating cylinder having an injection nozzle at a front end and a hopper at a back portion is included, a screw is inserted through the interior of the heating cylinder and a heating device (heater) is provided on the outer circumferential surface of the heating cylinder. In this way, a solid pellet supplied from the hopper into the heating cylinder is plasticized and kneaded through shearing produced by the rotation of the screw and heating produced by the heating cylinder, and thus the molten resin to be injected into the mold is generated. On the other hand, in terms of the multi-functionality of the heating device, a heating device is also proposed to which in addition to a general heating function, a forced cooling function is added.
Conventionally, as the heating device of an injection molding machine to which such a cooling function is added, a temperature control structure that is disclosed in patent literature 1 and that is preset in the back portion of the heating cylinder of the injection molding machine and a temperature control device that is disclosed in patent literature 2 and that is present in a heating cylinder having a heat retention cover-equipped heater are known. The temperature control structure that is disclosed in patent literature 1 and that is preset in the back portion of the heating cylinder of the injection molding machine has the purpose of making it possible to cool the temperature control on the back portion of the heating cylinder, thereby obtaining the same effect as that produced by the shortening of the heating cylinder and reducing the thermal history time of the raw material resin so as to prevent the physical properties from being degraded and to avoid a material biting failure and the insufficiency of a screw rotation torque. Specifically, between a heater for heating in the back portion of the heating cylinder and the heating cylinder, a cooling pipe is provided by being wound, and thus cooling water is passed.
The temperature control device that is disclosed in patent literature 2 and that is present in the heating cylinder having the heat retention cover-equipped heater has the purpose of reducing the amount of heat discharged from the heater and rapidly lowering the temperature of the heating cylinder. Specifically, a heat retention cover in which a heat retention material having a ventilation property is lined is attached to the outer wall surface of the heater attached to the heating cylinder, a half member in which a heat retention material is lined is coupled by a hinge portion to the heat retention cover so as to be freely opened and closed and when a tightening bolt screwed to a boss portion is tightened at the time of the attachment to the outer wall surface of the heater, both the half members are made to communicate with each other on the mating surface to form a ventilation path. Then, an inlet is provided in one of the half members, an outlet is provided in the other half member, a fan provided in the outlet is rotated to discharge air through the outlet, outside air is sucked through the inlet and thus air-cooling is performed.